"I want to host a couple clients sites"; "For what i want, which would you go for? I am also a beginner...."
How much access/control are you looking to provide your clients? Are there any specific features that either you or your clients need? For example, while ISP Config 3 is VERY popular, it does not provide LDAP support. Webmin/Virtualmin is another popular control panel.
IMHO (given that I, too, was a beginner to all of this only a few months ago) I'd recommend that you initially embark on this venture WITHOUT a control panel – in large part, b/c you already have a learning curve to climb w/VPSs; why add a 2nd learning curve in having to also learn the ins & outs of a control panel?
One of the HUGE benefits of DigitalOcean that I believe gets lost on a lot of beginners is the disposability of droplets. As you tread forward, make sure that you are taking a snapshot of your droplet every time you reach a milestone. That way, if you "f" something up later, you can easily (and, quickly!) spin up a new droplet and load your most recent image, so you won't be stuck having to start from scratch all over again.
In other words, with DigitalOcean, you can afford to push through a lot of trial 'n error w/o it costing you a fortune!